I've done three pair of EPOs with good results using the following process-

First sand down the surface of the rudder with 100 to 150 grit paper to knock off all the loose glass fibers (a sanding sponge/pad works best). Depending on how long the rudder was left in the sun, there can be a substantial amount of loose glass. Then wipe with acetone, and paint on a layer of epoxy (one side at a time). I used US Composites brand epoxy, but MAS or West would work fine as well. After full cure, the surface will have an amazing clearcoat finish which unfortunately you will have to sand away if you want to get the rudder super smooth (also, since the epoxy isn't UV stabilized, it needs a top coat of paint or it will deteroriate). So sand the rudder fair using 150 grit. You can add a second layer of epoxy and repeat if you end up blowing through the first coat. Then wet sand up to about 600 grit. Then I shot on a coat of flat black spray paint, allowed it to dry, wet sanded, sprayed on another coat of spray paint and wet sanded up to 1500 grit. Finally, I put on a coat of marine wax to make them shine. It takes a while, but the end result is quite nice.

SRM's method is basically the same that I have used to do a half doz or more sets over the years ... here are some minor differences ...

1) By hanging rudders vertically, you can coat both sides at once ...

2) When sanding use a (wood) sanding block to make sure that you have no 'ripples' ... check w/ the palm of your hand .... a lot !!!!

3) Recommend WHITE paint .... heat and UV's can deteriorate epoxy's quickly ... have you ever touched a black EPO rudder out in the blazing August sun??? HOT!!!! .... so paint them white .... drops the temp by a lot ... or .... keep them in your 'trailer storage box' when not actually being sailed ... also keeps them dry ...